Bibtool
takes multiple command line arguments to create an index of multiple
bibliography (.bib) files, and search for key names within the .bib
files. The first argument or arguments passed are the bibliography
files that need to be indexed. The file names entered must be case
sensitive and include the .bib extension. The .bib extension must be
either lower case or upper case and must coincide
with the actual file. A bibliography file with an extension
such as .BiB will not be indexed. Following the
bibliography files a index file name may optionally be
specified. If this file name is entered the index will be written
using the specified file name with a .ndx
extension. The bibs file (containing an index of .bib file names)
will be written with a .bfs extension. If
a index file name is not specified the last .bib file name will be
used, the .bib will be purged, and a .ndx and .bfs extension will be
added. The user may also specify a file containing key names,
authors, or titles to search for in the bibliography files. This
should be done by adding a -s followed by the file name containing
the key names to search for. If an author is being searched for a
single word from the authors name should be
preceded by an “a=” and a “t=” if it
is a title. If the -s [searchfile] is specified a searchfile.out
will be written to disk containing information about where the key
name was found. The program is ran with only bibliography filenames
as arguments it will only create the .ndx and .bfs index files of all
entries in the .bib files.

Additional
features include bibtool's ability to
ignore filenames that do not have a .bib extension and to accept .bib
filenames that do not exist followed by an error message to the user
that bibtool was not able to open the file. If one or more .bib
files fails to open it will continue to create the index files using
the bibliography file/files that are open-able.
It reports all instances of duplicate key names that it finds
in any of the .bib files. It is also able to report invalid
formating within the .bib files, such as if an entry does not end
properly when the end of the file is reached. It would then continue
to index the rest of the bibliography files. It is not recommended
that bibtool be used with key names that are more than 20 characters
in size. If they are more than 20 characters the characters
following the 20th will be truncated.